Personna theme, "X" to close chat window not showing, but still clickable

[signal15]

I have some custom CSS that puts a box around each category, but even with this disabled, the X or close button in the top right corner of chat windows does not show up. Edit: Looks like it only does it with the Flatly theme. If I go into my settings on this site and select Flatly, it does it here as well.